The present invention relates to a fire-resistant wall comprising at least one fire window, which is directly contiguous via its end faces with one face of an adjacent part of a construction wall, with the formation of a narrow joint, and which is fastened using fasteners placed on supporting arms and passing through holes made in the fire window.
Although the panes in a fire-resistant wall are usually fastened at their edges in a suitable frame, Patent EP 0,658,677 B1 teaches a construction wall structure in which multilayer fire windows, composed of several sheets of glass or panes and of layers of foaming material which expand with heat, these layers being placed between the sheets of glass or panes, are fastened, using clamping fixtures placed in the corners, by means of supporting arms to a support placed some distance from the fire window. If the adjacent parts of the construction wall are also composed of such fire windows, it is possible to produce in this way fire-resistant walls in entirely glazed constructions having an aesthetically pleasing appearance. The necessary sealing of the joints in the event of a fire, in order to prevent propagation of the fire and of the smoke, is then ensured, or alternatively enhanced, by the foaming mass emerging via the end faces of the multilayer fire windows.
In this known fire-resistant construction wall, the mass which is placed between the various panes of the multilayer fire windows and which foams in the event of a fire, forms a heat shield which greatly reduces the heat transfer through the fire window. In the event of a fire, that pane exposed to the fire in the stack of panes breaks as a general rule under the effect of the thermal stresses which are generated. On the other hand, that pane on the opposite side from the fire is heated markedly less and reaches temperatures of at most approximately 180xc2x0 C. It essentially retains its plane shape and expands in all cases in its plane under the effect of the heat. With known multilayer windows, having foaming interlayers, a bowing of the fire window can thereby occur only if the panes are assembled in a fixed manner to the support by means of fasteners and if the support and the pane expand very differently in the event of a fire. In order to prevent such a situation, the supporting arms carrying the fasteners are attached to the support so as to be able to slide along the support, thus preventing the panes from bowing.
A fire-resistant element for the closure of a room of this known type is relatively expensive because of the complicated structure of the multilayer fire windows which have an effective heat shield made of a foaming material between the panes.
On the other hand, the object of the invention is to develop a fire-resistant wall or construction wall, of the type mentioned in the introduction, in which more simply constructed fire windows can be used.
The fire-resistant wall in accordance with the invention is characterized in that the fire window is a pane without an interlayer capable of foaming, and in that the fasteners are attached to the supporting arms in a moveable or articulated manner such that they follow any bowing of the pane occurring in the event of a fire.
Unlike the known fire-resistant walls of the type mentioned in the introduction, which have multilayer fire windows, the physical conditions pertaining to the panes without a foaming interlayer, which is effective as a heat shield, are fundamentally different in the event of a fire. Whereas actually in the known multilayer windows the pane exposed to the fire breaks because of the thermal expansion and of the stresses resulting therefrom which act in the surface, thereby eliminating the compressive stresses on that side, the compressive stresses remain in their entirety in the hot face, for example in monolithic panes, as long as the fire window is fulfilling its function of a closure element of the room. However, this necessarily results, at least temporarily, in the pane bowing quite markedly, since that face of the pane which is on the opposite side from the fire is always at a lower temperature than the face exposed to the fire, because of the latter""s radiation and of the convection effect. At the present time, in order to prevent additional mechanical stresses due to the fasteners, under which additional stresses the mechanical strength of the pane, already subjected to high stresses, may easily be exceeded, the fasteners and/or the means for fastening them have, in accordance with the invention, a deformable structure and they adapt to any variation in the position of the pane, due to the bowing, at the respective fastening point.
It is certainly the case, according to a known principle, that it may be advantageous for the fire windows to be exposed uniformly, right to their edges, to the effect of the heat. However, the solutions known hitherto for obtaining uniform heating of the pane exclusively involve special frame constructions which are, for example, described in the publications DE 2,328,737 B2, DE 2,344,459 C3, DE 2,527,134 B2 and DE 2,654,776 C2.
The fire window may be of the monolithic type, having a pane which is constructed in such a way that, in the event of a fire, on the one hand it does not break under the effect of the stresses which are generated and on the other hand it has a softening temperature high enough not to become separated from its support. For this purpose, thermally prestressed (toughened or tempered) panes having the properties of monolithic safety glass are particularly used.
In this regard, it has proved particularly advantageous to use, for this purpose, panes having properties such as those described in Patent DE 19,710,289 C1. These panes of silicate glass are characterized in that they have a thermal expansion coefficient xcex120-300 of 6 to 8.5xc3x9710xe2x88x926 Kxe2x88x921, a thermal stress factor xcfx86 of 0.5 to 0.8 N/(mm2.K), a softening point (viscosity=107.6 dPa.s) of 750xc2x0 to 830xc2x0 C. and a forming point or working point (viscosity=104 dPa.s) of at most 1210xc2x0 C., preferably at most 1190xc2x0 C. The thermal stress factor xcfx86 is the quantity, specific to the glass, which is calculated from the thermal expansion coefficient xcex1, the elastic modulus E and the Poisson""s ratio xcexc by the formula xcfx86=xcex1E/(1-xcexc).
Of course, it is also possible to use, as fire windows, laminated windows consisting of at least two individual sheets of glass or panes which have been thermally prestressed or have been thermally prestressed partially and which have been assembled by means of the usual interlayers, especially of the polyvinyl butyral (PVB) type, not constituting a heat shield.
The individual panes of these laminated windows advantageously have thermal-expansion, softening, thermal-stress and working characteristics fulfilling the above conditions.
The pane of the fire window forming the wall according to the invention may advantageously be provided, at least on one side, with a layer that reflects the thermal radiation, this layer being advantageously deposited by pyrolytic deposition.
If, in a fire-resistant construction wall in accordance with the invention, the pane is for example fixed only in the corners by discrete supports, it may suffice, in the case of small sizes, for the discrete supports solidly prestressed with the pane to be provided with a ball joint or to be fastened to a ball joint, which allows the discrete support to undergo a pivoting movement in any direction. If, particularly in the case of larger sizes, the panes are held in their corners and furthermore also at points located between them, these intermediate fasteners must be made in such a way that they are supported so as to be able to move to some extent in the direction perpendicular to the surface of the pane, these intermediate fasteners being furthermore preferably supported in a pivoting manner.
In another advantageous embodiment of the invention, the materials filling the joints between the end faces of the pane and the adjacent parts of the construction walls are composed of heat-resistant substances which deform or expand in a manner such that the joints, which move and in certain cases enlarge as a consequence of the bowing of the pane, remain hermetically sealed throughout the period of resistance of the pane to the fire.
In this regard, it turns out that, for example, silicone rubbers crosslinking at high temperature, having a Shore A hardness of 40 to 60, as well as extruded beads composed of or using substances which foam under the effect of heat, namely, in particular, salts, which form, under the effect of heat, readily volatile substances such as water vapour, ammonia, carbon dioxide, etc., are very suitable for this use. The use of such substances as well as of certain adhesives which become ceramics at high temperature in order to close off the joints in fire-resistant construction walls is, in principle, known. It has also turned out that silicone sealing strips which are firmly bonded on one side, in a heat-resistant manner, to the end face of a pane and which bear against the opposite side, solely as a mechanical link, because of the shape and the friction force, to the end face of the adjacent part of the construction wall, and which slide along this face, while remaining hermetically applied thereto, throughout the bowing operation of the pane, are also very suitable.
Examples of substances that foam under the effect of heat may be found especially in WO-A-94/04355, WO-A-99/04970 or EP-A-590,978.